Setup `/src/CmakeLists.txt` for variable usage

The cmake file in the source directory is now using the variable project
name.

src/CMakeLists.txt

@@ -1,3 +1,8 @@
-add_executable(main
+add_executable(${PROJECT_NAME}
     main.c    
 )
+
+# Ensure the build rules are defined
+set_target_properties(${PROJECT_NAME} PROPERTIES SUFFIX ".elf")
+
+